An outbreak of influenza B in an isolated nomadic community in Jammu & Kashmir, India.

BACKGROUND & OBJECTIVES: Community outbreaks of disease amongst nomadic populations generally remain undocumented. Following a reported increase in acute respiratory tract infections (ARI) in May 2011 in a nomadic population of Sangerwini in Jammu & Kashmir, India, we examined the patients with ARI symptoms and their nasal swabs were tested for influenza virus. METHODS: Patients with ARI (n=526) were screened from May 14 to 23, 2011 and nasopharyngeal swabs collected from 84 with Influenza like illness (ILI) for bacterial cultures and influenza virus testing. Samples were tested for influenza A and influenza B by real time (RT)-PCR. RESULTS: Twelve (14.3%) of the 84 patients tested positive for influenza B, compared to only one (0.9%) of 108 patients with ILI in a parallel survey performed in Srinagar during the same period, suggesting a localized outbreak in the isolated nomadic community. All presented with respiratory symptoms of less than seven days. Familial clustering was seen in 40 per cent (25% of influenza B positives). Average daytime temperatures ranged from 15-16 ° C compared to 22 ° C in Srinagar. Four patients developed pneumonia whereas others ran a mild course with a total recovery with oseltamivir and symptomatic therapy. INTERPRETATION & CONCLUSION: Our report of confirmed influenza B in this underprivileged nomadic population argues for routine surveillance with efforts to improve vaccination and infection control practices.

Dynamic patterns of circulating seasonal and pandemic A(H1N1)pdm09 influenza viruses from 2007-2010 in and around Delhi, India.

Influenza surveillance was carried out in a subset of patients with influenza-like illness (ILI) presenting at an Employee Health Clinic (EHS) at All India Institute of Medical Sciences (AIIMS), New Delhi (urban) and pediatric out patients department of civil hospital at Ballabhgarh (peri-urban), under the Comprehensive Rural Health Services Project (CRHSP) of AIIMS, in Delhi region from January 2007 to December 2010. Of the 3264 samples tested, 541 (17%) were positive for influenza viruses, of which 221 (41%) were pandemic Influenza A(H1N1)pdm09, 168 (31%) were seasonal influenza A, and 152 (28%) were influenza B. While the Influenza viruses were detected year-round, their types/subtypes varied remarkably. While there was an equal distribution of seasonal A(H1N1) and influenza B in 2007, predominance of influenza B was observed in 2008. At the beginning of 2009, circulation of influenza A(H3N2) viruses was observed, followed later by emergence of Influenza A(H1N1)pdm09 with co-circulation of influenza B viruses. Influenza B was dominant subtype in early 2010, with second wave of Influenza A(H1N1)pdm09 in August-September, 2010. With the exception of pandemic H1N1 emergence in 2009, the peaks of influenza activity coincided primarily with monsoon season, followed by minor peak in winter at both urban and rural sites. Age group analysis of influenza positivity revealed that the percent positivity of Influenza A(H1N1)pdm09 influenza virus was highest in >5-18 years age groups (OR 2.5; CI = 1.2-5.0; p = 0.009) when compared to seasonal influenza. Phylogenetic analysis of Influenza A(H1N1)pdm09 from urban and rural sites did not reveal any major divergence from other Indian strains or viruses circulating worldwide. Continued surveillance globally will help define regional differences in influenza seasonality, as well as, to determine optimal periods to implement influenza vaccination programs among priority populations.

Genetic diversity of HA1 domain of hemagglutinin gene of pandemic influenza H1N1pdm09 viruses in New Delhi, India.

Genetic analysis of pandemic 2009 influenza A (H1N1; H1N1pdm09) virus was undertaken to understand virus evolution during 2009 and 2010 in India. Surveillance of influenza viruses from July 2009 to December 2010 revealed major peaks of circulating H1N1pdm09 viruses in August-September and December-January 2009 and then in August-September 2010. To understand the diversity of the H1N1pdm09 virus, selected specimens (n = 23) from 2009 or 2010 were characterized by nucleotide sequence determination of the HA1 subunit of the HA gene. Phylogenetic analysis revealed that 22 clustered with clade 7 viruses characterized by S203T mutations, whereas one virus from 2010 fell within clade 6. None of the viruses from either 2009 or 2010 formed a monophyletic group, suggesting a continuum of independent introduction of circulating viral strains. Amino acid analysis revealed minor amino acid changes in the antigenic or receptor-binding domains. Importantly, we observed mutations that were also present in 1918 pandemic virus, which includes S183P in 4 and S185T mutation in 3 of 13 viruses analyzed from 2010, while none of the 2009 viruses carried these mutations. Whether antibody-mediated pressure is imposing such changes remains to be determined. Continued genetic surveillance is warranted to monitor pathogenicity as the virus evolves to acquire new features.

Emergence of 2009A/H1N1 cases in a tertiary care hospital in New Delhi, India.

OBJECTIVE: To determine virologic and epidemiologic characteristics of pandemic (H1N1) 2009 at All India Institute of Medical Sciences (AIIMS) a tertiary care hospital in New Delhi, India. METHODS: Nasal and throat swabs from patients with febrile acute respiratory illness (FARI) from August to December 2009 (n = 1401) were tested for 2009A/H1N1 and seasonal influenza A viruses by real-time RT-PCR. RESULTS: Of 1401 samples tested, 475 (33·9%) were positive for influenza A, of these majority (412; 87%) were 2009A/H1N1, whereas the remaining 63 (13%) were seasonal influenza A (49 were A/H3 and 14 were A/H1). While co-circulation of 2009A/H1N1 and A/H3 was observed in August-September, subsequent months had exclusive pandemic influenza activity (October-December 2009). Pandemic 2009A/H1N1 emergence did not follow typical seasonal influenza seasonality in New Delhi, which normally peaks in July-August, but instead showed bimodal peaks in weeks 39 and 48 in 2009. The percent of specimens testing positive for 2009A/H1N1 influenza virus was found to be highest in >5- to 18-year age group (41·2%; OR = 2·3; CI = 1·6-3·2; P = 0·00). CONCLUSIONS: Taken together, our data provide high prevalence of pandemic 2009A/H1N1 in urban New Delhi with bimodal peaks in weeks 39 and 48 and highest risk group being the children of school-going age (aged >5-18).

Pandemic and seasonal influenza viruses among patients with acute respiratory illness in Kashmir (India).

BACKGROUND: With the emergence of pandemic influenza A (2009A/H1N1) virus in India, we sought to determine the prevalence and clinical presentations of seasonal and pandemic influenza viruses among acute respiratory illness (ARI) patients from Srinagar, a temperate climate area in northern India, during the peak winter season. METHODS: Combined throat and nasal swabs, obtained from 194 (108 male) presenting with ARI from January to March 2010 (Week 53-week 10), were tested by RT-PCR for influenza A and B, including 2009A/H1N1 viruses. HA1 gene of selected 2009A/H1N1-positive samples was sequenced, and phylogenetic analysis was carried out. RESULTS: Twenty-one (10·8%, age 15-80 years, median age 40 years) patients tested positive for influenza viruses: 13 (62%) for 2009A/H1N1 virus, 6 (28·5%) for seasonal influenza A (H3N2), and 2 (9·5%) for influenza B. Twelve of the 13 patients with 2009A/H1N1 presented with febrile ARI, and eight had associated comorbidities. All of the patients recovered. Phylogenetic analysis of HA gene (n = 8) revealed that all strains from Srinagar clustered in 2009A/H1N1 clade seven along with the other 2009A/H1N1 strains from India. Amino acid substitutions in the HA protein defining clade seven (P83S, S203T, and I321V) were found in almost all isolates from Srinagar. CONCLUSIONS: Both seasonal and 2009A/H1N1 viruses appear to be associated with ARI in Srinagar. The 2009A/H1N1 in Srinagar is genetically similar to globally circulating clade 7 strains, with unique signature sequences in the HA gene. Further investigations into ascertain the role of these mutations in possible alteration of the virulence and transmissibility of the virus are needed.